Electrode structure for electron-discharge devices



J 1927' w. F. HENDRY ELECTRODE STRUCTURE FOR ELECTRON DISCHARGE bEVICESFiled April 1. 192

Patented June 14, 1927.

UNITED STATES WILLIAM. FERRIS HENDRY, OF NEW YORK, N. Y., ASSIGNOR TOWESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK. N. Y., ACORPORATION OF NEW YORK.

ELECTRODE STRUCTURE FOR ELECTRON-DISCHARGE DEVICES.

Application filed April 1,

This invention relates to an electrode structure for electrondischarge-devices and the method of making the same. More particularly,it relates to a novel type of grid electrode for a vacuum tube, in whichcertain cross bars of the id have aniefiective width in the plane of t Ie grid less than their actual width.

The electrode structure of this invention will be described forconvenience in connection-with a vacuum tube of the three electrodetype, although it will be apparent that its utility is not limited totubes of any particular type.

As is well known in theart, the vacuum tube of the'threeelectrode typecomprises a thermioniccathode, ananode, and a control electrode whichusually, though not necessarily, is placed between the other twoelectrodes. The control electrode heretofore employed has usuallycomprised a plurality of parallel wires, to which have been fastened orwelded cross wires at regular intervals .so as to form a network orgrld. Such a grid,

7 however, is difficult and expensive to manufacture in any quantitybecause of the number of operations required in fastening the wiresacross at proper intervals on the framework. Some grids, for example,re-

quire as many as 150 welds or more to complete a single grid electrode.

It is proposed, as one form of this invention, to manufacture the gridelectrode out of a sheet of metal by punching apertures, preferablyrectangular in sha e, in the sheet atspaced intervals so that t e sheet,after the punching, comprises two side pieces with a plurality of crossbars or strips therebetween. The distance between, and the width of thecross bars will depend on the type of tube in which the grid is to beused. For low power tubes, such as those operating on a plate voltage of60 volts, a wldth of cross bars of. .031 inch, and a distance betweenthe cross bars of approximately .080 inch, has been found satisfactory.For high 'power tubes however, such as those operating on a p atevoltage of 275 volts, where.

the width of the cross. bars becomes quite a factor in determining theelectrical characteristics of the tube, it has been found that the widthof the cross bars should be about .008 inch, which is less than itispractical to make it by punching the grid from sheet meta 1920. SerialNo. 370,618.

In accordance with this invention, the use of a punched grid in a highpower tube is made possible by twisting the cross bars until the planesof the cross bars are at right angles to the plane of the electrode. Thecross bars of such a grid offer ractically no obstruction to the passage-0 electrons between the cathode and .anode, since the effective widthof each cross bar is now the thickness of a sheet of metal and not theactual width between the punches made originally in the sheet of metal.

This invention will be better understood by reference to'the followingdetailed description taken in connection with the accompanying drawings,in which Figure 1, represents a sheet of metal after a plurality ofrectangular apertures have been made therein to form a grid-likestructure.

Figure 2 represents the grid after the.

cross bars have been twisted until the planes of the cross bars are atright angles to the i plane of the id,

Figure 3 s ows the grid bent double, in order that 1t may be used in adouble-grid double-plate tube, such as that shown in F1 ure 4.

igure 5 illustrates 'a tool that may be employed-in twisting the crossbars of the grld; and

Figure 6 shows how the tube, of the t pe structure. The grid, as shown,comprises .two parallel side pieces, 8 and 9, which are connected by aplurality of cross bars 10, 11', 12, 13, and so forth. In themanufacture of a punched grid, such as that shown in Figure 1, it hasbeen found practically impossible to make the width of the cross barsmuch less than about .031 inch where the thickness of the sheet was only.009 inch.

Any attempt to make the cross bars of a much narrower width results inthe punching machine carrying away the cross bars with it. J

In. accordance with this invention, the use of a punched grid in avacuum tube, requiring cross bars of a narrower width than it ispossible to make them by the punching process, is made possible bytwisting the cross bars. Such a grid, with twisted cross bars, isillustrated in Figure 2. When the cross bars are twisted at right anglesto the plane of the grid, the effective width of each cross bar becomesthe thickness of the sheet metal employed, which, in the example cited.above, was only .009 inch.

It is evident that the cross bars may be twisted by any suitable means,such as pincers or the like. Figure illustrates a type of tool that maybe employed in twisting the cross bars. The tool comprises a handle, 16,attached to two stationary jaws, 17 and 18, the length of which isslightly less than the distance between the side pieces, 8 and 9. of thegrid. A slit between the two jaws, 17 and 18, is just sufiicient toreceive one of the cross bars of the grid.

Figure 3 represents the grid structure of Figure 2 bent so as to formtwo parallel portions, thereby adapting the grid to be employed in thedouble-grid double-plate tube shown in Figure 4. The tube, 20, comprisesa cathode. 21, two anode plates, 22,

23, and a grid electrode, 24, which may be of the punched grid typeillustrated in Figure 3.

Figure 6 shows how the tube 20 may be employed in an electric system torepeat and amplify currents from line 2727 to line 28-28. Space currentfor tube 20 is supplied by a battery, 30, while the cathode, 21, isheated by a battery, 31. The grid and cathode electrodes are connectedto the incoming line by a transformer 32, while the anode and cathodeare connected to the outgoing line 28-28 by a transformer, 33. Tube 20,connected up in such a manner,

will imprcss on line 28 28 amplified currents of the form received bythe tube from .the incoming line 27-27.

It is apparent that the unched grid with twisted cross bars, descri edabove, represents only one of various ways of manufacturing a gridhaving cross bars arranged so that the projection of each cross bar, onaplane parallel to the plane of the grid, is. less than the actual widthof each cross bar;

It is also apparent that this invention may be ap lied to grids of otherty es than that descrl ed above. Thus it is wit in the scope of thisinvention to make the cross bars in the well-known welded grid, have aneti'ective width in the plan-e of the grid less than their actual Width.Furthermore, this invention is not limited to types in which thedecrease in the effective width is accomplished by distorting the crossbars. Distorting the side pieces, for example, to make each in a zig-zagform, will produce the same result.

l/Vhat is claimed is: 1

1. The process of manufacturing a grid electrode out of a sheet ofmetal, which comprises forming apertures in said sheet, so

shaping the sheet that a plurality of the.

strips of metal remainingbetween said a ertures present an effectivewidth in the p ane of said grid less than the actual width of saidstrips, and bending said sheet to provide two parallel surfaces.

2. The process of manufacturing a unitary grid electrode out of a sheetof metal, which comprises punching apertures in said sheet, shaping thestrips of metal remain ing between the apertures to prevent the planesthereof substantially at right angles to the plane of the grid, andbending said sheet to provide two parallel surfaces.

3. The process of manufacturing a unitary grid electrode out of a sheetof metal, which comprises punching apertures in said sheet, placing thestrips of metal remaining between the apertures at an angle to the planeof the sheet, and bending said sheet to provide two parallel surfaces.

4. The process of manufacturing a grid electrode out of a sheet ofmetal, which comprises forming apertures in said sheet, shaping thesheet so that one of the strips of metal remaining between saidapertures has an effective width in the plane of said grid less than theactual width of said strip, and bending said sheet to provide a pair ofparallel surfaces.

In witness whereof, I hereunto subscribe W. FERRIS HENDRY.

